This invention relates generally to triggering arrangements for oscilloscopes, and in particular to a pattern recognition system for qualifying valid triggering conditions for digital storage oscilloscopes.
Typical digital oscilloscopes use a single level-crossing trigger detection to issue valid trigger signals to start or stop waveform acquisition. More sophisticated oscilloscopes employ a limited form of pattern recognition, such as waveform templates, or other information in which an input signal deviates from an expected pattern to qualify valid triggering events. This is known in the art as xe2x80x9cbaby-sittingxe2x80x9d to catch random anomalies, infrequent glitches, or other out-of-the-ordinary events. Such instruments are expensive and complicated to operate.
Many users are only interested in a stable image of an input signal to see whether or not something is wrong with the shape of the signal. For these users, operating the instrument is only a bothersome necessity. This is particularly true when the signals are complex waveforms and the user wishes to view only a portion of interest, such as television waveforms or waveforms generated by rotating machinery. Also, it would be desirable to trigger on anomalies, such missing pulses or wrong time intervals based on unpredictable timing of events. In particular, it would be desirable to have in a digital oscilloscope a flexible triggering system capable of triggering on a variety of pattern-related phenomena, such as a match (or mismatch) of time intervals, match (or mismatch) of signal amplitudes or waveshapes, or partial matching such as recognition of the sync and burst portions, while ignoring the video portions, of television signals.
In accordance with the present invention, valid trigger qualification in digital storage oscilloscopes may be established from recognition of triggering level and time interval information, as well as other pattern-related information, to start or stop waveform acquisition.
In the preferred embodiment, an acquisition logic circuit extracts a pair of triggering levels from peak-to-peak amplitude information of an input signal, and applies such triggering levels to a trigger generator that employs dual comparators and an RS flip-flop to generate raw triggers when the input signal passes through both triggering levels. The input signal is then analyzed in the presence of the raw trigger signals for pattern matches or mismatches. For example, pattern-related parameters may include time intervals between events, peak-to-peak amplitude, specific waveshapes or partial waveshapes, the number of pulses in a pulse train, or other quantifiable phenomena associated with signal patterns.
The smallest representation of a pattern may be described as time information in addition to trigger-level information. For example, triggering conditions may be established to issue a valid trigger signal, and thus start or stop waveform acquisition to subsequently store and display a waveform only when a raw trigger event occurs from a level crossing and when the interval of a signal matches a previously-established interval, or in certain situations when the interval fails to match a previously-established interval. Similarly, a triggering operation may be established to generate a valid trigger when an anomaly, such as an expected raw trigger falling outside a predetermined time zone or pattern, indicating an interval or pattern mismatch. Triggering on such a mismatch would permit this condition to be detected and stored.
The trigger recognition system of the present invention may further be extended to the occurrence of complex signals, such as those associated with television, rotating machinery, or other phenomena occurring in predetermined or known patterns.
It is therefore one feature of the present invention to provide a digital oscilloscope with automatic trigger qualification from pattern recognition.
It is another feature of the present invention to provide a system for automatically establishing valid triggering for a digital oscilloscope using triggering level and time information.
It is another feature of the present invention to provide an oscilloscope capable of triggering on signal anomalies, such as mismatching patterns.
Other features, and advantages of the present invention will become obvious to those having ordinary skill in the art upon a reading of the following description when taken in conjunction with the accompanying drawings.